Punching apparatus

ABSTRACT

A punching apparatus in which two tool portions come together to punch out a workpiece. At least one tool portion is mounted on a cylinder housing with one part of that tool portion fixed relative to the cylinder housing and another part movable relative to the cylinder housing. Such movement of the tool parts is provided by inner and outer piston systems in the cylinder housing. Either piston system can be fixed to the cylinder housing while the other remains movable relative to the cylinder housing. The movable part of the tool portion can be connected to either piston system, depending on which is arranged to be movable relative to the cylinder housing.

mted States Patent [151 3,646,116?

Axtmann Feb. 8, 1972 [54] PUNCHING APPARATUS 2,586,695 2/1952 Mueller..83/639 X [72] Inventor: Adam Axtmann, Burback, Gennany Primary EmminerAndrew R. Juhasz 731 Assignee: Maschinenfabrik Lorenz AG, EttlingenAssistant Examiner-Mon Gilden (Baden), Germany Attorney-Larson, Taylorand Hinds [22] Filed: June 15, 1970 57 ABSTRACT PP 46,341 A punchingapparatus in which two tool portions come together to punch out aworkpiece. At least one tool portion is A u Pri mounted on a cylinderhousing with one part of that too] por- [301 Forelgn pp cation onty tionfixed relative to the cylinderhousing and another part June 14, 1969Germany ..P 19 30 398.1 movable relative to the cylinder housing. Suchmovement of the tool parts is provided by inner and outer piston systemsin [52] US. Cl ..83/380', 83/390, 83/623, the cylinder housing. Eitherpiston system can be fixed to the 83/639 cylinder housing while theother remains movable relative to [5 l ]v Int. Cl ..B26d 5/42 thecylinder housing. The movable part of the tool portion can [58] Field ofSearch ..83/380, 390, 623, 639 be connected to either piston system,depending on which is I arranged to be movablerelative to the cylinderhousing. [56] References Cited 11 Claims, 3 Drawing Figures UNlTEDSTATES PATENTS r .h

3,0845 80 4/1963 Schmid PUNCHING APPARATUS BACKGROUND OF THE INVENTIONThis invention relates to a punching apparatus, and in particular itrelates to a punching press, especially for fine punching operations,wherein two opposing ram systems come together as tool portions on theram systems cooperating with each other to engage and punch a workpiecelocated therebetween.

In the case of fine punching and in contrast to "free cut" punching,before the actual punching step, the workpiece must be firmly clamped,that is, held in place in the immediate vicinity at which the punchingstep will take place in order to prevent the workpiece material frombeing drawn inwardly during the punching step and thusresulting in aninferior punched edge. This clamping of the outer portion of theworkpiece is normally accomplished by means of a raised annular ridgeprojecting outwardly from an outer part or matrix of the tool portion.However, depending on the shape, nature and size of the workpiece, thismatrix which carries the raised annular ridge and maintains the rawmaterial firmly clamped is exposed to large and variable stresses bothin the axial direction (that is, the direction of relative movement ofthe two ram systems) and in the radial direction (that is, in planesgenerally perpendicular to the axial direction). Moreover, in manycases, these forces will be out of balance, resulting in a large radialresultant force on the outer matrix carrying the annular ridge. In orderto obtain a perfect punched edge with the smallest possible surfaceroughness, it is therefore necessary to firmly hold this outer matrix ina holder or frame which supports it axially as well as radially, firmlyengaging the outer periphery of the ring about its entire circumference.For example, in the case of an annular outer matrix, the frame or holderwill be ring shaped. Such an encircling holder requires in turn anannular piston arrangement or system in the cylinder housing behind thetool so that the holder can be attached for movement with this annularpiston, relative to the cylinder housing, during the punching step.Moreover, in other cases, for example, where the resultant forces on theouter matrix are not as great, it is possible to eliminate thisencircling radial support holder. In this case, the outer matrix may beconnected to a more simple conventional piston in a cylinder housing forproviding the said relative movement of the outer matrix relative to thecylinder housing during the punching step.

Thus, at present, in order to utilize the outer or annular pistonarrangement for large loads and also the simple piston system for smallloads, it is necessary that the entire piston system be changed whenchanging over from one mode of operation to another, that is from alarge load operation to a small load variation, or vice versa. Suchextensive changeover operations are clearly time consuming, and hence,uneconomical.

Thus, there exists a need for improving the operation of a fine punchingapparatus for use with different types of punching operations.

SUMMARY OF INVENTION Thus, it is a purpose of this invention to providea new and improved punching apparatus which overcomes the disadvantagesof the prior art.

This purpose of the present invention is achieved by providing anarrangement wherein the changeover time between the different modes ofoperation is substantially reduced by constructing at least one of theram systems with a cylinder housing having two coaxial piston systemsmounted therein, that is, an annular outer piston system and an innerpiston system. The arrangement is such that either one of the pistonsystems can be arranged for movement relative to the cylinder housingwhile the other remains fixed relative to the cylinder housing.Therefore, the task of rebuilding the ram system when changing betweenmodes of operation is completely eliminated. Depending on the nature ofthe tool portion to be mounted on the ram system, it is only necessaryto arrange the inner and outer piston systems such that a selected oneis fixed to the cylinder housing and the other is movable relativethereto.

Since the invention has particular importance for fine punching pressesof the type including an annular ridge formed on a matrix for clampingthe workpiece material prior to the punching step, in the present caseit is preferable that the ram system having the matrix with the raisededge be the one mounted on the ram system having the coaxial,selectivelyusable piston systems.

The said piston systems may comprise an inneij elongated piston havingan enlarged pistonhead in a chamber in a cylinder housing and front andrear piston rods extending therefrom, the front rod extending toward thetool portion, and the annular piston system may comprise an annularpiston surrounding this front piston rod. For large load operations, theinner piston may be clamped to the cylinder housing. for example byscrews acting on the rear piston rod. In small load applications, theinner piston rod may be permitted to reciprocate while the annularpiston is clamped to the cylinder housing.

For large loads, a holder may be provided, which holder encircles theouter periphery of the outer matrix having the ridge thereon, and thisholder may in turn be rigidly secured to the annular piston. In smallload operations, the outer'matrix having the ridge thereon may beoperatively connected to the inner piston for movement therewith bysuitable means such as thrust pins extending axially from the outermatrix to the inner piston.

Thus, it is a purpose of this invention to provide a new and improvedfine punching apparatus.

It is another object of this invention to provide a fine punchingapparatus which is more efficient in that a process of changing over fordifferent types of punching operations is substantially simplified sinceit is not required to rebuild the ram systems of the punching apparatus.

It is another object of this invention to provide a new and improvedfine punching apparatus wherein at least one ram system thereof includesa cylinder housing having inner and outer coaxial piston systems formedtherein and wherein either of these piston systems may be fixed relativeto the cylinder housing, permitting the other. to move relative to thecylinder housing.

Other objects and advantages of the invention will become apparent fromthe detailed description to follow, together with the accompanyingdrawings.

BRIEF DESCRIPTION OF DRAWINGS DETAILED DESCRIPTION OF PREFERREDEMBODIMENT I Referring now to the drawings, likenumerals represent likeelements throughout the several views.

Referring to FIG. I, there is shown a frame 1 having mounted thereonright and left ram systems (as viewed in the drawings). The right-handram system comprises a carriage 2 mounted in the frame for axial,longitudinal movement by means of roller bearings 3. This ram systemalso includes a cylinder 4 and a piston 5 mounted therein. The piston 5includes three integrally connected portions, namely a ram portion 6, anenlarged central portion 6a, and a rear portion 6b.

The ram portion 6 is positioned within the carriage 2. Fluid lines 7 and8 direct pressurized fluid to different portions of the cylinder 4 onopposite sides of the enlarged piston portion 6b. In addition, a tubularprojection extends from the rear wall of the cylinder 4 into a chamber10 in the central piston portion 6a. Pressurized fluid through passage11 passes to a passage 11a in the tubular portion 9 to the chamber 10.

On the front end of the carriage 2 there is provided the tool portionassociated with the right-hand ram system. The elements comprising thistool portion are shown in FIG. 1 and are also shown schematically inFIG. 2. Basically, this tool portion comprises an outer annular matrix15 and a central matrix 19, both of which matrixes are nonyieldinglyconnected to the carriage 2 for movement to the left during the punchingprocess directly with the piston 2. Between the two matrixes is anannular punching member which is connected to the carriage 2 throughpiston rod 22 and yielding piston and cylinder unit 23 so that thispunching member 20 will yield as the carriage 2 is moved to the leftduring the punching process. The outer matrix 15 is nonyieldinglyconnected to the carriage 2 through spacing elements 15 and 18. Thecentral matrix 19 is nonyieldingly connected to the carriage 2 throughspacing element 17 which is connected to (and possibly formed integralwith) the spacing element 16. The punching member 20 is then yieldinglyconnected to the piston 22 through thrust pins 21 which engage the headof piston 22 and do not engage the spacing element 18 whereby the member20 can be moved inwardly (that is, to the right) relative to theelements 15 and 19. This right-hand tool portion is then mounted in anencircling holder 13 which is secured to the carriage 2 through bolts.Of course this holder 13 also assists in providing a nonyieldingconnection between the carriage 2 and the outer matrix 15.

The left-hand ram system comprises a cylinder housing 24 having acylinder chamber 24a formed therein. A piston 25 located in the chamber24a includes a rear piston rod 27 having a flange 29 formed thereon.Suitable means such as a screw 28 are provided for rigidly securing theflange 29, and hence the piston 25, to the cylinder 24. The piston 25also includes a front piston rod 30 which is surrounded by an annularpiston 26, the latter having a front radially projecting flange portion26a. A stop member 42 rigidly connected to the cylinder 24 by bolts 43engages this flange portion 260 to limit axial movement of piston 26.

Referring now to FIG. 2 as well as FIG. 1, the tool portion on thisleft-hand ram system comprises an outer annular matrix 33 and a centralmatrix 35. The outer matrix 33 has formed thereon the annular raisedgripping ridge 34 for holding the workpiece material to prevent the samefrom being drawn in during the punching step. In the mode of operationas shown in FIGS. 1 and 2, the inner piston 25 is fixed against movementrelative to the cylinder housing 24 while the piston 26 is permitted tomove relative to the cylinder housing 24. In this case, the matrixes 33and 35 are nonyieldingly connected to the piston 26 for movementtherewith while the annular punching member 32 is connected to thepiston 25 to remain stationary like the piston 25 during the punchingstep.

In this mode of operation, the outer matrix 33 having the annular ridge34 formed thereon is normally subjected to large radial and axialforces, and hence it is supported by a toolholder 36 which encircles theouter periphery thereof. Holder 36 is in turn rigidly secured to theannular piston 26 by means of bolts 37. The inner matrix 35 is thennonyieldingly connected to the piston 26 through a flange at the rearend of element 35 and a thrust element 39 which extends from this rearflange to a spacing element 40 which in turn engages the annular piston26. The annular punching member 32 is then nonyieldingly engaged withthe piston 25 through a flange 38, thrust pins 31, and a spacing element30a, the latter engaging the piston 25.

Accurate axial relative movement of the two ram systems is provided byguide pins 14 which extend from the toolholder 36 to a bore formed inthe toolholder 13.

Fluid passages 41 and 52 supply pressurized fluid to different parts ofchamber 24a. The selection of either passage 41 or 52 is determined byswitch 53 and this is in turn dependent upon which of the two piston 25or 26 is movable and which is fixed to the cylinder 24.

When the apparatus is arranged for the mode of operation as shown inFIGS. 1 and 2, the operation is as follows. A workpiece which may be inthe form of an elongated strip of material is fed into the space betweenthe two tool portions. For example, the strip S may be an endless stripwhich is fed (by means not shown) horizontally through the space betweenthe two tool portions. The two tool portions are then brought togetherrapidly by supplying fluid through lines 11 and 11a to the chamber 10until the tool portions reach a position whereat they just engage thestrip workpiece S as shown in FIG. 2. Fluid is then introduced throughfluid line 7 thereby utilizing the larger rear surface of portion 6b forcreating the necessary force for the actual punching step. Upon furthermovement of the carriage 2 to the left and the fluid introduced throughline 7, first of all the annular raised ridge 34 becomes impressed in,and thus firmly clamps the outer portion of the workpiece. As thecarriage 2 continues its movement to the left, the annular punchingmember 20 engages, through the workpiece, the annular punching member32. Since this latter punching member cannot move, the members 20 and 32are at that point prevented from undergoing further movement to theleft. However, elements 33 and 35, by virtue of their connection to themovable yieldable annular piston 26, will continue to move to the leftunder the force of the moving carriage 2, the force being exertedthrough outer matrix 15 and central matrix 19 to the outer matrix 33 andthe central matrix 35. This constitutes the actual punching step withthe outer portion of the strip S and a central waste portion B moving tothe left with the desired article W remaining between the elements 20and 32. The finished article W is then ejected during the return strokeof carriage 2 as the member 20 moves to the left relative to thematrixes 15 and 19 and the matrix 35 acts as ejector for the centralwaste portion B.

FIG. 3 illustrates the different mode of operation wherein the forcesacting on the outer matrix 33 are not as great and hence it is notnecessary to use the more complicated mounting arrangement of FIGS. 1and 2. Specifically, it is desired to eliminate the elements requiring anonyielding engagement between the outer matrix 33 and the annularpiston 26 and instead to provide a nonyielding engagement between theouter matrix 33 and the inner piston 25. First, the screws 28 areremoved from the inner piston 25. First, the screws 28 are removed fromflange 29, thereby permitting reciprocating movement of piston 25.Switch 53 is then operated so that fluid will be introduced through line52 rather than line 41. Bolts 44 are then provided for rigidly securingannular piston 26 to the cylinder housing 24. The tool portion of thelefthand ram system is then removed. Specifically, elements 30a, 31, and36 through 40 are then removed and replaced by the elements shown inFIG. 3. Also, the tool elements 33, 32, and

' 35 are replaced by tool elements 47, 46 and 49, respectively.

A spacing member 51 is positioned at the right end of front piston rod30. The simplicity of FIG. 3 relative to FIG. 1 is apparent. Engagementbetween the outer matrix 47 and the yielding piston 25 is provided bymeans of thrust pins 50 which engage the member 51 while the centralmatrix 49 directly engages the member 51. Nonyielding engagement of themember 46 with the fixed piston 27 is provided by means of a holder 45which surrounds the tool and is engaged with the piston 26 by means ofbolts 370. This arrangement also includes guide pans 14 for providingaccurate relative movement between the two ram systems.

Only the portions of the ram systems forming the pressing part are shownin FIG. I, the other parts such as the details of the drive arrangement,being omitted for purposes of clarity since they do not form a part ofthe present invention. Although the elements are shown as being drivenhydraulically, other types of drives are possible, for example,mechanical drives, combinations of mechanical and hydraulic drives, etcetera. The tool portions shown herein illustrate the formation of anannular punched article. However, other tool shapes providing othertypes of articles are clearly within the scope of the invention. Forexample, irregular articles may be punched. Also, while the punch shownin this embodiment is closed in that the punchlines are closed circles,the invention may also be used for open cuts" wherein the punchlineextends to the outer periphery of the workpiece.

Although the invention has been described in considerable detail withrespect to a preferred embodiment thereof, it will be apparent that theinvention is capable of numerous modifications and variations apparentto those skilled in the art without departing from the spirit and scopeof the invention.

I claim:

housing, inner and outer relatively movable coaxial piston 1. A punchingapparatus comprising, aframe, first and systems mounted in the cylinderhousing, each piston system operatively connected to at least one partof the tool of the first ram system, said inner and outer piston systemsbeing constructed such that either one of them can be fixed to thecylinder housing to prevent movement of that fixed piston systemrelative to the cylinder housing while the other piston system ismovable relative to the cylinder housing, whereby relative movement ofthe inner and outer piston systems assist in the punching of theworkpiece when the two ram systems are brought together.

2. A punching apparatus according to claim 1, the tool portion of thesaid first ram system including an annular outer matrix, an annularraised ridge on said outer matrix projecting therefrom toward the secondrarn system, whereby when a workpiece is placed between the two toolportions of the ram systems, and when the tool portions are broughttogether, the annular ridge is impressed in the workpiece materialbefore the punching begins to prevent the workpiece from being pulledinwardly from said matrix during punching.

3. A punching apparatus according to claim 2, including means foroperatively connecting said outer matrix to the outer piston system formovement therewith during punching when the outer piston system isarranged to be movable relative to the cylinder housing, and foroperatively connecting the outer matrix to the inner piston system formovement therewith during punching when the inner piston system isarranged to be movable relative to the cylinder housing, and foroperatively connecting the outer matrix to the inner piston system formovement therewith during punching when the inner piston system isarranged to be movable relative to the cylinder housing.

4. A punching apparatus according to claim 3, wherein the means foroperativelyconnecting the outer matrix with the outer piston systemincludes a toolholder supporting the matrix radially and axially, andmeans for operatively connecting the toolholder to the outer pistonsystem for movement therewith.

5. A punching apparatus according to claim 4, including an inner matrix,means for operatively connecting the inner matrix with the outer pistonsystem for movement therewith when the outer matrix is connected to theouter piston system for movementtherewith, said inner and outer matrixesbeing separated by a punching member operatively connected to the innerpiston system such that the punching member does not move relative tothecylinder housing.

. 6 Apunching member according to claim 3, wherein the means foroperatively connecting the outer matrix with the inner piston systemincludes thrust pins acting as spacing elements between the outer matrixand the inner piston system such that the outer matrix moves with theinner piston system when the two ram systems are brought together.

7. A punching apparatus according to claim 6 including an inner matrix,means for operatively connecting the inner matrix with'the inner pistonsystem for movement therewith when the outer matrix is connected to theinner piston system for movement therewith, said inner andouter matrixesbeing separated by a punching member operatively connected to the outerpiston system such that the punching member does not move relative tothecylinder housing.

8. A punching apparatus according to claim 1 including a stop memberconnected to the cylinder housing and arranged to limit movement of theouter piston system relative to the cylinder housing.

9. A punching apparatus according to claim 1 wherein said air pistonsystem comprises an axially extending piston having a pistonhead in acylinder formed in the cylinder housing and including a first piston rodextending from the piston towards the tool portion and including a rearpiston rod extending from the piston in a direction opposite from thetool portion, and including means for fixing the rear piston rod to thecylinder housing.

10. A punching apparatus according to claim 9 wherein said outer pistonsystem comprises an annular piston surrounding the front piston rod ofthe inner piston, and including means for rigidly connecting the outerannular piston to the cylinder housing.

11. A punching press according to claim 10 including a first fluidpassage for delivering fluid to the cylinder housing when the outerpiston member is fixed to the cylinder housing, and including a secondfluid passage for delivering fluid to the cylinder housing when the airpiston member is fixed to the cylinder housing, and including a switchfor delivering pressurized fluid to either one of said passagesdepending on which of said piston systems is fixed relative to thecylinder housing.

1. A punching apparatus comprising, a frame, first and second ramsystems mounted on said frame for relative movement axially towards andaway from each other, means on each of said ram systems for holding aportion of a punching tool such that when the two ram systems arebrought together the two tool portions cooperate with each other topunch a workpiece, at least said first ram system comprising a cylinderhousing, inner and outer relatively movable coaxial piston systemsmounted in the cylinder housing, each piston system operativelyconnected to at least one part of the tool of the first ram system, saidinner and outer piston systems being constructed such that either one ofthem can be fixed to the cylinder housing to prevent movement of thatfixed piston system relative to the cylinder housing while the otherpiston system is movable relative to the cylinder housing, wherebyrelative movement of the inner and outer piston systems assist in thepunching of the workpiece when the two ram systems are brought together.2. A punching apparatus according to claim 1, the tool portion of thesaid first ram system including an annular outer matrix, an annularraised ridge on said outer matrix projecting therefrom toward the secondram system, whereby when a workpiece is placed between the two toolportions of the ram systems, and when the tool portions are broughttogether, the annular ridge is impressed in the workpiece materialbefore the punching begins to prevent the workpiece from being pulledinwardly from said matrix during punching.
 3. A punching apparatusaccording to claim 2, including means for operatively connecting saidouter matrix to the outer piston system for movement therewith duringpunching when the outer piston system is arranged to be movable relativeto the cylinder housing, and for operatively connecting the outer matrixto the inner piston system for movement therewith during punching whenthe inner piston system is arranged to be movable relative to thecylinder housing, and for operatively connecting the outer matrix to theinner piston system for movement therewith during punching when theinner piston system is arranged to be movable relative to the cylinderhousing.
 4. A punching apparatus according to claim 3, wherein the meansfor operatively connecting the outer matrix with the outer piston systemincludes a toolholder supporting the matrix radially and axially, andmeans for operatively connecting the toolholder to the outer pistonsystem for movement therewith.
 5. A punching apparatus according toclaim 4, including an inner matrix, means for operatively connecting theinner matrix with the outer piston system for movement therewith whenthe outer matrix is connected to the outer piston system for movementtherewith, said inner and outer matrixes being separated by a punchingmember operatively connected to the inner piston system such that thepunching member does not move relative to the cylinder housing.
 6. Apunching member according to claim 3, wherein the means for operativelyconnecting the outer matrix with the inner piston system includes thrustpins acting as spacing elements between the outer matrix and the innerpiston system such that the outer matrix moves with the inner pistonsystem when the two ram systems are brought together.
 7. A punchingapparatus according to claim 6 including an inner matrix, means foroperatively connecting the inner matrix with the inner piston system formovement therewith when the outer matrix is connected to the innerpiston system for movement therewith, said inner and outer matrixesbeing separated by a punching member operatively connected to the outerpiston system such that the punching member does not move relative tothe cylinder housing.
 8. A punching apparatus according to claim 1including a stop member connected to the cylinder housing and arrangedto limit movement of the outer piston system relative to the cylinderhousing.
 9. A punching apparatus according to claim 1 wherein said airpiston system comprises an axially extending piston having a pistonheadin a cylinder formed in the cylinder housing and including a firstpiston rod extending from the piston towards the tool portion andincluding a rear piston rod extending from the piston in a directionopposite from the tool portion, and including means for fixing the rearpiston rod to the cylinder housing.
 10. A punching apparatus accordingto claim 9 wherein said outer piston system comprises an annular pistonsurrounding the front piston rod of the inner piston, and includingmeans for rigidly connecting the outer annular piston to the cylinderhousing.
 11. A punching press according to claim 10 including a firstfluid passage for delivering fluid to the cylinder housing when theouter piston member is fixed to the cylinder housing, and including asecond fluid passage for delivering fluid to the cylinder housing whenthe air piston member is fixed to the cylinder housing, and including aswitch for delivering pressurized fluid to either one of said passagesdepending on which of said piston systems is fixed relative to thecylinder housing.